Mikael Karlsson Group

B cell biology team

Antibodies produced by B cells protect us from invading pathogens such as virus and bacteria but they can also induce harmful reactions and play a key role in many of the major diseases affecting humanity. For example, in autoimmune diseases they take part in the destruction of the tissue and organs affected, and in allergy they participate in the activation of the acute inflammatory response that can sometimes be fatal. The objective of our research effort is to define the mechanisms behind activation and regulation of the antibody production in disease through a B cell perspective. In recent years it has become evident that the pre-immune B cell repertoire consists of functional subtypes that differ not only in their anatomical location but also in their antibody repertoires, and thresholds for activation. We investigate how these B cell subtypes are recruited and regulated via their interactions both with antigen presenting cells and different types of T cells. In addition we investigate other effector mechanisms mediated by B cells including their ability to secret inflammatory mediators. The goal is to gain understanding how to interfere with mechanisms leading to faulty antibody production and other B cell mediated activities that add to disease development. To do this we will use a translational approach and combine observations from clinical cohorts with experimental mechanistic in vitro and in vivo investigation

The picture summarizes the focus of our research. The nature of the antigen (Ag): self vs non-self will directly or indirectly affect B cell activation, including T cell dependency. The B cell will interact with different immune cells, including APCs and various innate lymphocytes that regulate access to antigen and provide soluble factors. Also Pattern Recognition Receptors (PPRs) such as scavenger receptors will influence the outcome of B cell activation and behavior.

Current projects and directions of our research

Mikael Karlsson graduated from Uppsala University 1997 and received his Ph.D. in 2000 from the same University where he studied under Prof. Birgitta Heyman. In 2005 he completed his postdoctoral research at the Rockefeller University in New York in the lab of prof. Jeffrey Ravetch. After this he joined the faculty at Dept. of Medicine at Karolinska Institutet, Stockholm receiving an Assistant prof. position appointed by the Swedish Research Council. In 2009 he became Associate professor and in 2010 he received a senior research position appointed by the Swedish Research Council. Since 2016 he is a Professor of Immunology at the department of Microbiology, Tumor and Cell biology. Dr Karlsson is an elected member of the Henry Kunkel Society of Immunology as well as a co-chair of the Swedish Society for Immunology and head of the KI inflammation and immunology network (KiiM).

Eva Hellqvist, Postdoc: Left the lab in 2015 for a second postdoc at department of Medicine, Huddinge, Karolinska Institutet.

Mattias Forsell, Postdoc: Left the lab in 2015 for a position as Assistant Professor at Umeå University.

Kajsa Prokopec, Postdoc: Did a joint postdoc with Harvard Med. School the lab of Prof. Michael Carroll. Kajsa left the lab in 2014 to do a second postdoc at the department of Medicine, Solna, Karolinska Institutet.

Yunying Chen, Postdoc/Assistant Professor: Left the lab in 2014. Yunying studied innate B cell activation in Allergy and Autoimmunity and left to pursue a continued science career in the biotech industry.

Emilie Grasset, PhD: Dissertation 2013, Karolinska Institutet. Thesis: Regulation of B cell Responses to Modified Self (opponent: Prof. John Kearney, University of Alabama, USA). Emilie left the lab for Postdoc at Mount Sinai School of medicine, New York, USA, supported by the Swedish Research Council.